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101.
Lukas Stolzer Antonina Vigovskaya Prof. Christopher Barner‐Kowollik Dr. Ljiljana Fruk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(41):14309-14313
A photochemical approach based on nitrile imine‐mediated tetrazole‐ene cycloaddition is introduced to functionalize gold nanorods with biomolecules. For this purpose, a bifunctional, photoreactive linker containing thioctic acid as the Au anchoring group and a tetrazole moiety for the light‐induced reaction with maleimide‐capped DNA was prepared. The tetrazole‐based reaction on the nanoparticles’ surface results in a fluorescent pyrazoline product allowing for the spectroscopic monitoring of the reaction. This first example of nitrile imine‐mediated tetrazole‐ene cycloaddition (NITEC)‐mediated biofunctionalization of Au nanorods paves the way for the attachment of sensitive biomolecules, such as antibodies and other proteins, under mild conditions and expands the toolbox for the tailoring of nanomaterials. 相似文献
102.
Spacer‐Modulated Differentiation Between Self‐Assembly and Folding Pathways for Bichromophoric Merocyanine Dyes 下载免费PDF全文
Dr. André Zitzler‐Kunkel Eva Kirchner David Bialas Christian Simon Prof. Dr. Frank Würthner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14851-14861
We have synthesized a large series of bis(merocyanine) dyes with varying spacer unit and investigated in detail their self‐organization behavior by concentration‐ as well as solvent‐dependent UV/Vis spectroscopy. Our in‐depth studies have shown that the self‐organization of the present bis(merocyanine) dyes is subtly influenced by the nature of the spacer unit. The utilization of rigid spacers results in the formation of self‐associated bimolecular complexes with high binding strength, while flexible spacers drive the respective bichromophoric dyes to intramolecular folding. Our thorough investigations on the impact of alkyl spacer chain length on the folding tendency of the present series of bis(merocyanine) dyes revealed a biphasic behavior, that is, a steep increase of the folding tendency for the dyes containing C4 to C7 chains and then a gentle decrease for dyes with longer alkyl spacer chains as evidenced by free energy (ΔG) values for the folding of these dyes. Furthermore, analyses of aggregates’ optical properties based on exciton theory as well as quantum chemical calculations suggest a bimolecular aggregate structure for the dye possessing a rigid spacer and a rotationally twisted pleated structure for the bis(merocyanine) dyes having spacer units with less than seven carbon atoms, while the application of longer alkyl chain linkers (≥C7) provides enough flexibility to orient the chromophores in electrostatically most favored antiparallel fashion. 相似文献
103.
Cover Picture: A Modular Synthesis of Conformationally Preorganised Extended β‐Strand Peptidomimetics (Chem. Eur. J. 42/2015) 下载免费PDF全文
104.
《Angewandte Chemie (International ed. in English)》2017,56(8):2035-2039
One‐pot cascade annulations among nitrosoarenes, alkenes, and N‐hydroxyallylamines have been achieved with CuCl/O2 catalysts, forming fused oxazinane/isoxazolidine heterocycles with excellent diastereoselectivity (d.r. >20:1). To enhance the synthetic utility, we developed a successive cleavage of the two N−O bonds of the resulting heterocycles. A mechanism involving dipolar [3+2] cycloadditions of nitrone intermediates with their tethered alkenes is postulated for formation of these heterocycles. 相似文献
105.
Synthesis and Anti‐HIV Activity of Triazolo‐Fused,Medium‐Sized Cyclic Nucleoside Analogs Prepared by an Intramolecular Huisgen 1,3‐Dipolar Cycloaddition 下载免费PDF全文
Jingbo Sun Rongwang Liu Qiang Fu Jian Zang Qiangqiang Tao Jinchang Wu Hui Zhu 《Helvetica chimica acta》2014,97(5):733-743
Medium‐sized cyclic nucleosides containing a fused triazole ring were synthesized via intramolecular Huisgen 1,3‐dipolar cycloadditon reaction. 2′,3′‐seco‐Uridine was employed as the key intermediate for the introduction of azido and alkynyl moieties in the defined positions of the reaction precursors. The cycloaddition reactions were achieved in high yields by heating the precursor in refluxing toluene. The uracil base in these target compounds was successfully transformed to the corresponding cytosine. The synthesized compounds were evaluated in a MAGI assay for their anti‐HIV activities, and in a H9 T lymphocytes assay for their cell toxicities. 相似文献
106.
Synthesis of Spirocyclic and Tricyclic Isoxazoline via 1,3‐Dipolar Cycloaddition Reactions 下载免费PDF全文
1,3‐Dipolar cycloadditions of the bicyclic monoterpenes (S)‐(?)‐camphene ( 1 ), (R)‐(+)‐a‐pinene ( 2 ), and (S)‐(?)‐b‐pinene ( 3 ) with aryl and heteroaryl nitrile oxides afforded new spirocyclic and tricyclic isoxazoline derivatives 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 whose biological activities were evaluated in bioassay studies. 相似文献
107.
An efficient and stereoselective synthesis of diaza-triquinanes, the skeleton structures of many natural products, has been accomplished by intramolecular 1,3-dipolar cycloaddition of azomethine imine generated from sugar-derived hex-5-enal and pyrazolidin-3-one. 相似文献
108.
Middleton DA 《Magnetic resonance in chemistry : MRC》2011,49(2):65-69
Solid‐state nuclear magnetic resonance (SSNMR) is a powerful technique for the structural analysis of amyloid fibrils. With suitable isotope labelling patterns, SSNMR can provide constraints on the secondary structure, alignment and registration of β‐strands within amyloid fibrils and identify the tertiary and quaternary contacts defining the packing of the β‐sheet layers. Detection of 14N? 13C dipolar couplings may provide potentially useful additional structural constraints on β‐sheet packing within amyloid fibrils but has not until now been exploited for this purpose. Here a frequency‐selective, transfer of population in double resonance SSNMR experiment is used to detect a weak 14N? 13C dipolar coupling in amyloid‐like fibrils of the peptide H2N‐SNNFGAILSS‐COOH, which was uniformly 13C and 15N labelled across the four C‐terminal amino acids. The 14N? 13C interatomic distance between leucine and asparagine side groups is constrained between 2.4 and 3.8 Å, which allows current structural models of the β‐spine arrangement within the fibrils to be refined. This procedure could be useful for the general structural analysis of other proteins in condensed phases and environments, such as biological membranes. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
109.
The complete analysis of the complex (1)H NMR spectra of some monosubstituted cyclobutanes was achieved to give all the (1)H chemical shifts and (n)J(HH) (n = 2, 3 and 4) coupling constants in these molecules. The substituent chemical shifts of the substituents in the cyclobutane ring differ significantly from those in acyclic systems. For example, the OH and the NH(2) groups in cyclobutanol and cyclobutylamine produce a large shielding of the hydrogens of the opposite CH(2) group of the ring compared with little effect on the comparable methylene protons of butane. These effects and the other (1)H shifts in the cyclobutanes were modelled successfully in the CHARGE program. The RMS error (calculated vs observed shifts) for the 34 (1)H shifts recorded was 0.053 ppm. The conformational equilibrium in these compounds between the axial and the equatorial conformers was obtained by comparing the observed and the calculated (4)J(HH) couplings. These couplings in cyclobutanes, in contrast to the corresponding (3)J(HH) couplings, show a pronounced orientation dependence; (4)J(eq-eq) is ca 5 Hz and (4)J(ax-ax) ca 0 Hz. The couplings in the individual conformers were calculated at the B3LYP/EPR-III level. The conformer energy differences ΔG(ax-eq) vary from 1.1 kcal mol(-1) for OH to 0.2 kcal mol(-1) for the CH(2)OH substituent. The values of the conformer energy differences are compared with the previous IR data and the corresponding theoretical values from molecular mechanics (MM) and DFT theory. Generally, good agreement is observed although both the MM and the DFT calculations deviate significantly from the observed values for some substituents. 相似文献
110.
Xiaofang Li Haochong Liu Bin Liu Aiting Zheng Guobin Li Xianyong Yu Pinggui Yi 《中国化学》2011,29(4):741-744
The 1,3‐dipolar cycloaddition reactions of nitrilimine with thiazolo[3,2‐a]pyrimidine derivatives was investigated. Bis‐cycloadducts were obtained through a domino 1,3‐dipolar cycloaddition/ring‐opening/ring‐opening/1,3‐dipolar cycloaddition processes. The structures of the products were characterized thoroughly by NMR, IR, MS, elemental analysis together with X‐ray crystallographic analysis. 相似文献